WERE indigenous Australians the world's first surfers? That's a question posed by John Ogden, a surfing documentary filmmaker and author of a new book about the surf culture of Sydney's northern beaches.

Two years ago, Ogden published Portraits from a Land Without People - a comprehensive pictorial history of Aboriginal Australia. His latest, lavishly illustrated volume - Saltwater People of the Broken Bays, which is launched today by the actor Jack Thompson - was meant to be less academic. ''But as I researched, I realised very little had been done on the first people who lived between North Head and Barrenjoey Head,'' says Ogden, who spent his youth as a correspondent for surfing magazine Tracks.

''These were very good water people, with excellent surf skills. It was their livelihood. Theirs was a canoe culture and they were known to take these craft out in large surf. They fished with spears or lines and hooks and would dive off rock ledges into the surf. Their traditional way of life broke down within a couple of years of the arrival of the First Fleet, mainly due to smallpox.''

White Australians only ''discovered'' the joys of the beach around the 1880s, he says. ''The English might have ruled the waves in 1788, but none of them could really swim.

''It would take another 100 years before we started to feel comfortable in the surf.''

Surveyors such as William Govett were obviously impressed. In the 1830s, while fishing for snapper at Newport Reef, Govett lost the fishing line he had borrowed from an Aborigine. To Govett's amazement, the Aborigine ''stood upon the verge of a rock … plunged through a rising wave and disappeared'', staying under water ''full a minute'' before emerging with hook and line intact, riding ''a heaving surge'' back onto the rock.

Ogden says there are many similar stories of indigenous men and women repeatedly diving considerable depths for abalone or crayfish.

The Europeans were scathing about the ''flimsy craft'' the Aborigines built out of gum trees, and they certainly seemed puny compared with the First Fleet ships. Yet these canoes were clearly strong enough to survive the Pacific surf.

''There are quite a few reports of mothers taking babies out into the surf in their canoes,'' Ogden says.

''Children got used to the water from a very early age.''

The most contentious claim Ogden makes is that the Saltwater People had also mastered surfing. ''They could body surf, and many people regard that as the purest form of surfing.''

Hawaiians were the first to build surfboards and to invent surfing as a recreation, Ogden says. But he points out the similarity between what experts now believe indigenous canoes looked like and the modern surf ski.

Ogden commissioned a local artist, Michael Glasheen, to draw what the scene might have looked like in 1787 as a Kayimai man from the Manly area emerges from the water with his canoe at what is now Fairy Bower.

''No one should rule it out,'' Ogden says. ''Why wouldn't they take a free ride to the beach after fishing?''